I just like to utilize the fact that Gardevoir looks fit to be a dancer. :3

Hmm. Use Psychic first, just to get a good hit on him.

Then use Shadow Sneak to fade into the shadows, and wait until the last possible moment before you strike.

Then use Psychic once more.

Use Magic Coat on any status moves, and use Snatch to steal any self-targeting moves (bar rest)

Psychic ~ Shadow Sneak ~ Psychic
Subs: Magic Coat & Snatch

yeah, yeah, yeah, I'm using cheap subs. That'll only be for the first turn fighting a freaking rotom, I almost-promise.